Until now, environmental changes have mainly been detected by sensors which pass on state information via wire lines, and are at the same time supplied with electrical power via these wire lines. The wiring, which is often complex and thus costly, is problematic in this case.
Battery-operated sensors are likewise known, which pass on the corresponding measured values by radio. However, these have the disadvantage that the batteries must be serviced. Particularly where there are a large number of devices to be monitored, the batteries cause logistic problems for servicing, as well as high costs.
DE 198 26 513 A1 discloses an automation system for control of a processing apparatus having a radio sensor which is used to reduce the installation complexity. For this purpose, it has a radio sensor which can be operated by means of a solar cell, possibly in conjunction with an energy store.
One object of the present invention is to provide an improved capability for power-saving status checking, which can be implemented such that it can be installed easily.
This and other objects are attained in accordance with one aspect of the present invention directed to a sensor system having at least one voltage generator for conversion of non-electrical energy to electrical energy, for example a solar cell, an inductive element or a piezoelement. There is therefore no need for a battery to operate it. The voltage generator is followed by at least one energy store, for example a rechargeable battery or a capacitor. The energy store is connected to at least one voltage converter, which converts the stored energy to an output signal which is suitable for operation of a processor controller. For example, the voltage converter could cut off voltage peaks which would damage the processor controller. In addition, at least one sensor is provided which detects the desired state, for example a light intensity sensor, a contact sensor or a position sensor. Furthermore, at least one transmitter is provided for wire-free transmission of transmission messages, in particular in the form of radio signals. The transmission messages can be produced by means of the processor controller and contain at least one measured value from the at least one sensor. However, they may also contain two or more measured values, for example from two or more sensors.
The sensor system also contains a timer circuit, which can be triggered as a function of a state value, for example of a voltage level, of the at least one energy store, and which activates the sensor system in order to transmit at least one transmission message after a time interval which is determined by it.
In accordance with an embodiment of the invention, the time interval may, for example, either be fixed and predetermined by the design of the timer circuit or may be redefined variably on each activation by the processor circuit. For this purpose, in particular, the state of charge of the energy store may be checked and included in the definition of the transmission frequency per unit time, in order to allow the sensor to be operated for periods which are as long as possible. After its activation, the energy should typically be sufficient to operate the running timer circuit even if the external energy supply then fails, for example if it becomes cloudy and a solar cell is being used.
It is particularly advantageous if the sensor can also be operated as a voltage generator, because this allows the number of components to be reduced, and thus the susceptibility to faults.
It is advantageous for at least one voltage generator to be a solar cell, because this allows for an energy supply which operates throughout the year. The solar cell is particularly advantageous for illumination measurement because, in this case, it can be used as a voltage generator and as an illumination sensor at the same time.
It is also advantageous for at least one voltage generator to be a piezoelectric transducer and/or an inductive converter, because this provides a low-cost energy source. Particularly in the case of position finding, for example for doors, windows and the like, it is advantageous for this voltage generator to be used as a sensor for position finding at the same time. It is advantageous in order to achieve a long operating life for a solar cell also to be provided as a voltage generator.
In order to achieve a long time interval and/or to provide two or more activation cycles even when the energy supply is low or has failed, it is advantageous for the timer circuit to have semiconductor modules based on ULP (“Ultra Low Power”) technology.
In order to identify the sensor, particularly when two or more sensors and/or sensor systems are used at the same time, it is advantageous for the transmission message also to contain at least one identification code.
Furthermore, the above-mentioned object is achieved by a monitoring system which contains at least one sensor system as described above, as well as at least one receiving and evaluation system. The sensor system typically passes information on by means of the transmission message without the use of wires, for example by radio, to a receiving and evaluation system which is connected to the electrical mains system. The receiving and evaluation system is, for example, an illumination controller, or it contains display elements, bus systems and/or actuators (louvre control etc.). The receiving and evaluation system may advantageously monitor two or more sensor systems.
The above-mentioned object is also achieved by the use of the sensor system and/or of the monitoring system for position finding, for example for windows, doors or other moving devices in buildings. This use is becoming increasingly important for reasons related to safety, energy saving and in order to increase the convenience in both commercial premises and in the field of private dwellings. In this case, it is advantageous if the sensor can also be used as a voltage generator, particularly if it contains an inductive or piezoelectric element. Other elements, for example electrostrictive or magnetostrictive elements, are also generally feasible.
The above-mentioned object is also achieved by the use of the sensor system and/or of the monitoring system for illumination signaling, with the voltage generator and the sensor in particular at least partially including the same solar cell; the solar cell is then used as a combined voltage generator and illumination sensor. The illumination intensity at workstations, in commercial premises, in private households, on public roads, in public squares, and in installations etc. is being controlled to an increasing extent as a function of the daylight incidence, in order on the one hand to achieve optimum lighting quality and in order on the other hand to save energy. The discovery makes it possible, for example, to switch on the illumination in the outdoor area or in buildings.
The sensor system and the monitoring system will be explained schematically in more detail in the following exemplary embodiments.